114 MORPHOLOGY AND EYOLUTION
differ from the African forms, in which 'the frontal articulates with the squamosal, thus separating the parietal and alisphenoid. The infra-temporal crest is
The zygoma conceals the slightly recurved coronoid
process of the mandible, and it sometimes shows the suture where the malar and temporal bones articulate. It is continued upwards and backwards above the long^
bonv, external auditory meatus,
»f * •"
Norma Basalis.—The bony palate has the usual
hypsiloid, or U-shaped, form; but the relative proportions of length and width vary, as pointed out by Delisle (244). The differences are probably age changes, and are similar to the age changes which occur in the Chimpanzee and Gorilla. The sutures between the premasillas and maxillae disappear early, and the anterior palatine foramina may be obliterated. The suture between the palatal processes of the maxillae may persist, and the maxillary-palatine sutures are irregular. The palate bones are perforated by the posterior palatine foramina in all specimens; but there are variations in the characters of the posterior nasal spine. That process may be small, absent, or replaced by two small spicules of bone.
The pterygoid plates of the sphenoid diverge so as to include a wide fossa, as in the Gibbon, and the hamular processes are likewise small. The alisphenoid is tunnelled by the foramen ovale, but there is no aiisphenoid canal for the internal maxillary artery. The suture between the basi-sphenoid and basi-occipital is irregular.
The glenoid fossa is shallow, but is bounded behind